Synaptic mechanisms of inhibition represent some of the greatest gaps in our understanding of the processing of acoustic signals in the brainstem. The subtypes of neurons, with whom they interconnect, the efficacy of those connections, and how the size and shape of the inhibitory signals are controlled, all these remain unclear. Given the relation between inhibition as a target for drugs and disease in other brain regions it seems likely that a deep knowledge of inhibitory systems will be of clinical relevance for treating auditory disorders. In this proposal, we will address decisively each one of these points, focusing on the ubiquitous inhibitory neurotransmitter glycine. First, we will take advantage of the availability of lines of mice in which green fluorescent protein (GFP) is expressed in subsets of inhibitory cells to reveal the function and connectivity of common subtypes of auditory neurons that have been rarely studied using direct electrophysiological means. Second, we will identify mechanisms that control the duration of the inhibitory state, and focus on the role of transmitter clearance from the synaptic cleft and the promising role of GABA/glycine cotransmission in regulation of glycinergic decays. Finally, we will determine what mechanisms set whether glycine excites or inhibits postsynaptic neurons.